Heretofore, a honeycomb structure made of cordierite and including a loaded catalyst has been used in the treatment of harmful substances in an exhaust gas discharged from a car engine. Moreover, it is also known that a honeycomb structure formed by using a sintered silicon carbide body is used in the purification of the exhaust gas (e.g., see Patent Document 1).
When the exhaust gas is treated by the catalyst loaded onto the honeycomb structure, it is necessary to raise a temperature of the catalyst to a predetermined temperature. However, at the start of the engine, the catalyst temperature is low, and hence there has been the problem that the exhaust gas is not sufficiently purified.
In consequence, there has been investigated a method of disposing a heater made of a metal on an upstream side of a honeycomb structure onto which a catalyst is loaded, to raise a temperature of an exhaust gas (e.g., see Patent Document 2).